Police discovered potentially incriminating evidence in a Cadillac belonging to the grandmother of Michael Boatwright, the alleged shooter who killed XXXTentacion.

On Thursday (Aug. 9), TMZ reports the vehicle contained two "dark colored" masks, .22 caliber ammunition, an assault rifle and multiple gun cases, according to a search warrant reviewed by the website. The recovered ammo reportedly matches the brand and caliber of casings found at the scene of XXXTentacion's fatal shooting outside a motorsports dealership in Deerfield Beach, Fla. on June 18.

Boatwright is one of four suspects charged with first-degree murder for their alleged role in the rapper born Jahseh Onfroy's death. X was shot in the driver's seat of his black BMW while parked outside Riva Motorsports, and was pronounced dead shortly after at Broward Health North hospital.

A grand jury indictment, citing an affidavit based on surveillance footage and recollection from an alleged witness, claims an SUV approached X's black BMW outside the dealership, when two men, wearing a red and black mask, respectively, each armed with guns, exited the SUV and approached the rapper in an attempted robbery.

The indictment claims Boatwright shot XXXTentacion, and four individuals fled in the SUV after removing a small bag containing cash from the rapper's car.

Boatwright, 22, is currently in custody and was recently ordered to undergo a mental evaluation to determine whether he has the capacity to understand the severity of his charges and potential punishment.

Earlier on Thursday (Aug. 9), Trayvon Newsome, whom the Broward Sheriff's Office believes to be the second armed assailant, pled not guilty to his own charges of first-degree murder and armed robbery.