Up-and-coming rapper Luci4 was found dead in an L.A. residence on Sunday … and now we’re learning more about his movements hours prior to his death.

We broke the news … the rapper — best known for his viral hit “BodyPartz” — was found dead at a friend’s house at the age of 23. His cause of death has yet to be determined … and his family wants answers.

The father of Luci4 — born James Dear IV — tells TMZ … last Saturday, his son was running late to catch a 10:52 PM flight to Miami for a concert.

There was a pre-boarding issue with TSA … and James got super upset, which is when his father says LAX Police got involved — and he was detained.

About 20 minutes later, James called his grandmother to say he was no longer detained — and if there wasn’t another flight, he’d drop by her home for fresh clothes. He never showed … and the next day, Feb. 22, Luci4 was found dead.

The family has reached out to the airport authorities for more information … such as what exactly did Luci4 do — and who was with him.

The family suspects foul play since James’ wallet, they say, was found empty inside the home — his cash and ID were gone.

His cause of death is currently listed by the L.A. medical examiner as “deferred.” LAPD did not send homicide detectives to the scene … and said the case was with the coroner.

The family created a GoFundMe, which reads in part … “He touched the lives of so many with his creativity, kindness, and desire to share with others. Even though he did not reach all of his dreams, the impact he left on those who knew him is immeasurable.”