Police on Thursday arrested the father of a Mastery Charter student who had been charged with murder after accidentally shooting his 18-year-old twin brother with a handgun that allegedly belonged to their father.

Aleem Gillard, 42, was charged with involuntary manslaughter, possession of a weapon by a convicted felon, endangerment and corruption of minors, police said Friday.

On Wednesday, charges of murder and related offenses were dropped against Fayaadh Gillard, 18, in the Dec. 1 fatal shooting of his twin, Suhail, at their father’s Overbrook home in the 1100 block of North 63rd Street.

District Attorney Larry Krasner said the twins’ father had been showing his sons and his 16-year-old daughter how to use two guns when one went off.

After the shooting, Aleem Gillard instructed the two surviving children to lie about what happened, Krasner said.

“We believe Aleem Gillard is responsible for the death of his child Suhail, and he will be treated accordingly,” the district attorney said Wednesday. “Upon further and careful investigation, we have concluded while Fayaadh did pull the trigger, he did not do so with criminal intent. This was a horrific accident for which the whole family will suffer, but for which he should not be held criminally liable under these circumstances.”

The twins were seniors and football players at the Mastery Charter School Lenfest Campus at 35 S. Fourth St. in Old City, where Suhail Gillard was described by fellow students as a star football player. Police have said the brothers lived in Frankford.

Staff writer Robert Moran contributed to this article.