The team issued a statement on Mark's death:
"The LA Galaxy and the Southern California soccer community are deeply saddened by the passing of Galaxy Academy player Tommy Mark on Monday, April 16. Tommy was a tremendous young man who was loved by his family, his friends and his teammates. The entire LA Galaxy family is mourning his loss. Our thoughts are with his family at this time."
The cause of death was not disclosed.
A fan account for Los Angeles FC, where Mark played during the 2016-17 season, tweeted condolences while noting a career highlight for Mark:
The Galaxy will honor Mark with a minute of applause before Saturday's game against Atlanta United at the StubHub Center. The team will also wear black armbands in his memory.