A Florida sex offender is behind bars after authorities allege his girlfriend's 8-year-old son found his gun and accidentally shot his little sister

A Florida felon is behind bars after authorities allege his girlfriend’s 8-year-old son found his gun and accidentally fired it this weekend — killing the boy’s younger sister — according to multiple reports.

Maurice Mobley, 34, was arrested Sunday in Jacksonville, Florida, on a charge of possession of a firearm by a felon, according to jail records.

According to First Coast News, WJXT and WOKV, Mobley brought a handgun into his girlfriend’s Jacksonville apartment and her son got access to it on Saturday and unintentionally shot his sister and a 4-year-old neighbor boy.

The girl, identified in local reports as Serenity Allen, was killed in the shooting while the boy was injured and is expected to make a full recovery, Jacksonville sheriff’s officials said at a Saturday news conference.

The shooting was reported about 1 p.m. Saturday, the sheriff’s Chief Chris Butler said. It was not immediately clear how the boy got to the gun, when it was brought into the apartment, what measures had been taken to secure it or how it went off.

Butler said the gun was fired once, hitting both victims. The boys then reportedly ran to a neighbor for help.

The victim and her older brother had been left alone for an “undetermined” period of time while their mother went to the store, Butler said.

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Mobley later turned himself in investigators, declining to speak about the charge against him, according to local reports. He remains in custody on a $200,000 bond and is scheduled to appear in court on Feb. 28, according to jail records.

It was unclear Monday if he has retained an attorney or entered a plea, according to court officials.

According to state records, Mobley is a registered sex offender in Florida in connection with a 2001 case involving sexual misconduct with a child under the age of 16.

Efforts to reach Serenity’s family were unsuccessful Monday. But neighbors and relatives say they are grappling with what authorities called a “tragic” shooting.

“Every time I see her [Serenity’s mom], she always has her kids. If you go in her house, there’s a house full of food. That’s a good mama,” one neighbor told WJXT. “So all that we’re seeing on Facebook, Instagram and stuff talking about she’s bad — no she is not. She is a good mom in my Bible, my book.”

One of the victims’ grandmothers told the station, “The only thing I can say right now is I’m praying. I want God to work this out. I feel horrible for them. This is a horrible thing, for anybody to have to go through.”