The Google engineer who was killed when a deadly avalanche hit Mount Everest was given heartbreaking letters from friends and loved ones before he left - and told not to read them until he reached the summit. Dan Fredinburg was one of four Americans killed when a massive earthquake struck Nepal on Saturday, causing a wall of ice and rock to engulf the base camp. The 33-year-old, who was with three colleagues and had been navigating the area for Google Maps, was given the messages by his girlfriend Ashley Arenson just before he set off on the expedition. Dan Fredinburg was one of three Americans killed when the massive earthquake struck Nepal on Saturday, killing more than 3,700 people. He was given letters by friends and family when he reached the summit . The 33-year-old Google engineer was given the letters by his girlfriend Ashley Arenson just before he left . It isn't known whether he got a chance to read them. His friends have since uploaded a CrowdRise page in Fredinburg's memory, with all the funds going to relief efforts. More than $36,000 has been raised so far. Close friend Max Stossel posted a picture of the letter he wrote to his late friend on Saturday alongside a tribute. 'We lost one of my dearest friends yesterday. One of the most wonderful human beings any of us would have the pleasure of knowing,' he said. 'Dan is the most interesting, adventurous, human I've ever known. He was a silent force for justice in the world in a way I thought only existed in fiction, someone who cared about others so much that he sometimes had trouble looking them in the eye. 'Someone who created fun and mischief out of thin air. Someone who broke up fights by walking into the middle of them and dancing with both fighters. Someone who I think about almost every day, through the lens of "What would Dan do?". 'Before his climb, Ashley asked some of his friends and family to write letters to take up to the top with him. I hope he got a chance to read this one, and if he didn't, I hope he can somehow feel it now, along with the unbelievable amount of love and stories being shared around the world in his honor. His friend Max Stossel posted a picture of the letter he wrote to his late friend on Saturday alongside a tribute. In it he said: 'Your story has already greatly impacted mine for the better' In a tribute on Facebook, Stossel added that Fredinburg was 'one of the most wonderful human beings any of us would have the pleasure of knowing' Before embarking on his expedition, Fredinburg took part in a Puja ceremony in Kathmandu, to make sure 'all of his energies were aligned' As he approached the base camp he was given a black medallion and had his face slapped by rice and flour to grant him 'the wisdom and appearance of age' The letter read: 'Dan (dan dan dan) 'You must be really high up for this written Echo (echo echo). Everyone you know and love is eventually going to die (die die die). When we do, we leave behind our stories. 'Those stories are told and passed on, impacting the lives of others until they are stories (stories stories stories). 'Your story has already greatly impacted mine for the better. With each adventure you return with stories that most people wouldn't dream of experiencing themselves (selves selves selves). 'Thank you for pushing the human race to be greater, more daring, and to truly live life rather than survive it (it it it). 'I love you, brother. Please return safely with stories (stories stores). 'And even if you don't... We'll all be horrified, saddened, and heartbroken, that we can't create new stories with you but we'll also know that you've already lived the equivalent of at least 100 lifetimes. 'You are a f****** champion. Safe, wonderful & breathtaking journey. 'Love, Max Stossel (ossel ossel).' Elia Saikaly, a documentary maker from Ottawa, Canada, was at the Everest base camp when the avalanche hit. He described the dramatic moment he began looking for survivors and realized Dan was dead. Speaking to CBC, he said: 'I saw two of them, and I went up to them and I hugged them and I asked them if they were OK and they said yes. And I turned around and I said, "Where's Dan?" And there was this silence and there was this pale look. All they said was, "He didn't make it," and it was as if all time just stood still.' 'And I was in a complete daze and I was in shock, and I just couldn't believe it. They had to be kidding. He was gone, just like that. ... It's a nightmare that you just want to wake up from.' Fredinburg started at Google in 2007. Beforehand he graduated from the Arkansas School of Math, Science and Art in Hot Springs in 1999, before moving on with his career. When he started at the technology company as product manager and the head of privacy at Google X, the company's secretive arm best known for 'moonshot' projects such as the self-driving car. He had been working on mapping Everest since 2013, meaning those interested in adventuring and expeditions could look up routes themselves. It is part of 'Google Adventure', a branch of the company that creates routes for users in extreme locations. His colleague Laurence You released a statement on Saturday saying: 'I just had the immensely sad task of sending the following to all Google employees. My thoughts are with everyone in Nepal, and with Dan's family and friends. 'Early this morning, Nepal experienced the worst earthquake in its history, registering 7.8 on the Richter Scale. Current reports are that over 1,000 people were killed. It's a terrible tragedy. 'Sadly, we lost one of our own in this tragedy, Dan Fredinburg, a long-time member of the Privacy organization in Mountain View, was in Nepal with three other Googlers, hiking Mount Everest. He has passed away. Fredinburg used to be in a relationship with One Tree Hill and Chicago PD actress Sophia Bush. The pair are pictured together at the Do Something Awards in 2013 . He uploaded a picture of himself relaxing in his tent on Day 16 of his trip . The Google engineer uploaded this picture while attending Burning Man in the Black Rock Desert, Nevada . 'The other three Googlers with him are safe and we are working to get them home quickly.' Google said it has launched a 'person finder' tool for Nepal to help people find loved ones in the aftermath of the quake and 'is working to get updated satellite imagery to aid in the recovery effort.' Google says it is committing $1 million to the quake response. Fredinburg was in a relationship with One Tree Hill and Chicago PD actress until last year. She paid tribute to her ex-boyfriend when the news of his death surfaced. She wrote on Instagram: 'There are no adequate words. Today I find myself attempting to pick up the pieces of my heart that have broken into such tiny shards, I'll likely never find them all. Today I, and so many of my loved ones, lost an incredible friend. 'Dan Fredinburg was one-of-a-kind. Fearless. Funny. A dancing robot who liked to ride dinosaurs and chase the sun and envision a better future for the world. His brain knew how to build it. His heart was constantly evolving to push himself to make it so. 'He was one of my favorite human beings on Earth. He was one of the great loves of my life. He was one of my truest friends. 'He was an incredible brother, a brilliant engineer, and a damn good man. I'm devastated and simultaneously so deeply grateful to have known and loved him, and to have counted him as one of my tribe. I was so looking forward to our planned download of "all the things" when he got home. 'I am crushed that I will never hear that story. I am crushed knowing that there are over 1,000 people in Nepal suffering this exact feeling, knowing that they too will never hear another tale about an adventure lived from someone that they love. Disasters like this are often unquantifiable, the enormity is too much to understand. 'Please remember that each person who is now gone was someone's Dan. Please remember that our time on this Earth is not guaranteed. Please tell those you love that you do. Right now. This very minute. And please send a kiss to the sky for my friend Dan. 'His energy is so big and so bright, and it's all around us, so put some love toward him today. And then hug your loved ones again.' New Jersey-born Dr Marisa Eve Girawong, 29, was also killed when ice and rock crushed the 18,000-foot-altitude base camp where she worked as a medic for Madison Mountaineering. A third American, Tom Taplin, 61, who owned TET Films & Photography, was making a documentary when the earthquake hit. Vin B Truong was confirmed as the fourth victim.
Dan Fredinburg was one of three Americans killed in the earthquake . 33-year-old was head of privacy at Google X and once dated Sophie Bush . Friend Max Stossel wrote a heartbreaking letter to him before he left . He said: 'Your story has already impacted mine for the better' Fredinburg was one of four Americans killed when the earthquake hit Nepal .