Former NFL star Aqib Talib's brother, Yaqub Talib, is a wanted man in Texas -- this after cops say he was involved in a fatal shooting at a youth football game this weekend.

The Lancaster Police Department fired off an announcement Sunday saying that they were looking for Yaqub in connection to the death of an adult male Saturday ... who was shot and killed during an argument at the conclusion of a match that parents were angry about.

The man is said to be a coach for one of the teams ... there's a name circulating online, but we'll refrain from ID'ing him at this time until the family and/or cops confirm. In any case, he succumbed to his injuries ... which police say was a direct result of a discharged firearm.

There's video of the alleged shooting which eyewitnesses claim shows a man pull out the gun and fire. We're told people in the crowd identified the man wearing all-black and a bucket hat as possibly being one of the Talib brothers -- but it's hard to make out who this person is, or if they have a weapon at all. What is depicted ... a scuffle/apparent shooting.

Lancaster PD says they've identified the suspect in this case as Yaqub, and note there's an active warrant for his arrest. It's unclear what charge, exactly, they wanna bring him in on ... but some say this looks to be outright murder. We've reached out to LPD for clarification.

A former mugshot of Yaqub was attached to the press release, and Lancaster is asking for any and all help in finding him. BTW, Aqib was also there for this tragic killing.

His attorney tells TMZ ... "Aqib was present when this unfortunate incident occurred and is very distraught and devastated over this terrible loss of life. He would like to convey his condolences to the family of the victim and to everyone who witnessed this unfortunate tragedy."

Aqib famously played for the Bucs, the Broncos (with whom he won a Super Bowl ring) and several other teams over the years. He was not named in Lancaster PD's release.