FORT WORTH (CBSDFW.COM) – A Tarrant County Grand Jury has indicted the former boyfriend of a woman who was killed in her home as her two children hid in another room.

Nathaniel Mitchell, 34, was indicted on charges of Murder, Burglary with the Intent to Commit Aggravated Assault, and Burglary with the Intent to Commit Assault in the death of Donna Alexander.

“The children locked themselves in their rooms. They were afraid,” described Alexander’s sister, Lauren Armour.

Nathaniel Mitchell (photo credit: Tarrant County Jail)

“He broke in her bedroom window because he was beating on the door and they wouldn’t let him in,” said Armour.

Mitchell initially told Grand Prairie police that Alexander fell in the shower. Mitchell’s indictment said he hit her “with an unknown object” or “pushed her” causing her to “strike an unknown object” resulting in her death.

Donna Alexander (photo credit: CBS News)

Alexander was an advocate for domestic violence survivors. She received local and national media attention as founder of the Anger Room, a facility that allowed visitors to alleviate stress by breaking items in rooms mocked up to look like a workplace or living area.

“Her legacy is bigger than the Anger Room. She taught people how to love unconditionally,” said Alexander’s best friend Torria Bradford.

Alexander hoped to expand her Anger room brand to additional cities in Texas and on the East Coast.

“My sister made an impact. She had a big heart. She just wanted to help everybody,” said Armour.

♥ National Domestic Violence Hotline

Mitchell was originally charged with aggravated assault, but the charge was upgraded to murder when Alexander died.

Mitchell remains in custody of the Tarrant County Jail.