The Chiefs star QB and the NBA legend both sent out emotional tweets after learning that D'Sean Perry, Lavel Davis and Devin Chandler had been shot and killed in a horrifying incident on the UVA campus on Sunday night.

James called it "Sad Sad Sad" with a crying emoji ... while Mahomes wrote simply, "Prayers for @UVAFootball."

Dozens of other athletes have sent their condolences to the trio's family members and the Cavaliers' community in wake of the deaths ... with Julian Edelman calling it all a "sad sad day in Virginia."

"If we don't do anything, nothing changes," the former New England Patriots star said on his Twitter page. "This has to stop. Now."

Former NFL star and UVA alum Thomas Jones added in a tweet of his own that he was "sending love & light to the families & friends of the victims as well as the entire #VirginiaFootball program."

Arizona Cardinals star DeAndre Hopkins also shared his condolences ... and acknowledged how Davis' last Instagram post was about a play he made during Sunday's game against the Rams.

"My prayers go out to the whole UVA community today. Especially to the families, friends, and fans of Lavel Davis Jr., D’Sean Perry, and Devin Chandler," he said.

"These men were taken too soon and for no reason. The last post on Lavel’s story was a play from my game yesterday and it is a reminder that everyday here on this earth is a blessing and a gift. Make the best of it. Rest In Peace my brothers 🖤."

As we reported, officials say Perry, Davis and Chandler were all killed after they were shot on a bus in a UVA parking structure after they had just returned from a class field trip.

Police say former Cavalier running back Christopher Darnell Jones Jr., who left the team over a year ago but remained a student on campus, was the gunman.