The live-in boyfriend of the creator of the Anger Room, a Dallas warehouse where people can cope with stress by smashing things, is suspected of her murder, according to police.

Donna Alexander, 36, died days after 34-year-old Nathaniel Mitchell assaulted her, Grand Prairie police said.

Police said the incident happened inside Alexander's home in Grand Prairie on Sept. 21.

Alexander was taken to Baylor Scott & White Hospital in Grand Prairie with severe injuries and police said she died the following Monday.

Officers interviewed Mitchell and arrested him at the hospital on outstanding warrants.

Hours later, detectives charged him with aggravated assault. However, they upgraded the charge to murder once Alexander died.

Mitchell is being held in the Tarrant County Correction Center on $250,000 bond.

"He used the thing that God gave us all, his hands, that were meant to heal ... and he used them as a weapon toward my child," said Dalfinne Lassiter, Alexander's mother.

Donna Alexander, a mother of two, opened the well-known business the Anger Room in Deep Ellum after first starting the business in her Dallas garage in 2008.

Those at the Anger Room are given protective equipment and a bat and allowed to destroy items like plates and televisions in rooms set up to simulate a kitchen, workplace or living area.

"Some people like running or jogging and boxing," Alexander told NBCDFW last year. "Others come to the Anger Room to break some stuff and then leave happy."

Family said that Alexander decided to create the Anger Room after being exposed to domestic violence herself. It was something she always advocated against.

"The fact that she ended up leaving this life with something she was against is mind-boggling," said her sister, Lauren Armour.

Lassiter said that Alexander donated seven of her organs to woman around the age of 30.

"She saved seven lives, but she's gone," Lassiter said.

Family said a vigil will be held Monday at 6 p.m. at Cole Park in Dallas.

DOMESTIC VIOLENCE HELP: Anyone affected by domestic violence, including friends and family members concerned about a loved one, can receive confidential help, advice, information or crisis intervention by calling the National Domestic Violence Hotline at 1-800-799-7233 or visiting the website thehotline.org, which offers a live chat service.