XXXTentaction's short career had been overshadowed by alleged incidents of domestic violence and at the time of his death he was facing 15 felony charges.
Onfroy released his debut album, 17, on August 25, 2017.
Police said the 20-year-old was leaving the dealership when he was approached by two armed suspects.
Videos of what appeared to be Onfroy unresponsive in the driver seat of a vehicle circulated on social media Monday. Reports say his run-ins with law enforcement also included two robberies, assault with a deadly weapon and witness tampering.
Initially, the Broward County Fire Department told the website that XXXTentacion was rushed to a hospital, but wouldn't elaborate on his current condition.
Following the sudden death of rapper XXXTentacion on Monday, celebrities flooded social media to honor the late artist. The controversy has resulted in numerous articles calling for the greater music industry to not "co-sign", or endorse, his music, including one that was published by Pitchfork titled, "XXXTentacion Is Blowing Up Behind Bars". A video appeared to show him punching a pregnant woman - his lawyers said the video was "completely in jest" - and he was awaiting trial in the beating of his pregnant girlfriend. TMZ reported that a judge recently granted his request to be let off house arrest so he could tour. His 2018 follow-up? (Question Mark) debuted at No. 1 and spawned the hit single "SAD!", which reached No. 7 on the Billboard Hot 100 chart. More updates will be added as they come.
And J. Cole said, in part: "RIP X. Enormous talent and limitless potential and a strong desire to be a better person".