XXXTentacion's Alleged Murderer is in Custody

The suspect's name is Dedrick D. Williams, and Broward County Sheriff's Dept. took the 22-year-old into custody Wednesday and booked him for first-degree murder.

During a vigil Wednesday night in South Florida ... X's mother told family and friends she'd just gotten notice from police that they'd made the arrest.

Someone at the gathering mentioned there was a chase on the nearby highway I-95 ... which may have ended with cops arresting Williams for the murder of X.

Williams was also charged with a probation violation for a previous grand theft charge. It's reported he is being held without bail.

XXXTentacion's murder happened in broad daylight, and there were several witnesses who reported seeing 2 masked men flee the scene.

The police also had surveillance videos to go on during the investigation.