Zamar Kirven -- a former starting LB for the Univ. of Houston football team -- has been accused of murdering his ex-H.S. teammates in a violent shooting Sunday.

The McLennan County Sheriff's Office said Kirven opened fire on 2 men, who may have been asleep at the time, at around 2 A.M. in Mart, Texas.

Officials did NOT release a motive for the alleged attack ... but they did say Kirven grew up with the men and even played high school football with them.