The Anaheim Police Department said, in a press release, that officers found Mateus dead on March 17 around 2:24 p.m. in an apartment building after "receiving reports of suspicious circumstances." Authorities did not say who owned the apartment, who made the call or how she was killed.
"Homicide detectives responded to the scene and determined that Mateus was murdered and identified Romo as the suspect," the department noted.
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Mirelle Mateus, 24, was allegedly killed by her ex-boyfriend in Anaheim. (Anaheim Police Department)
"Later that day, Romo was arrested in Riverside County and was ultimately booked at the Anaheim PD Detention Facility for murder."
The Mateus family couldn't be reached, but the victim's sister, Sandy, said in a statement posted to a GoFundMe that Mirelle was a "very special, caring and generous person with a heart so pure and full of love" and her death "shattered" her family's hearts.
About four months earlier, on Dec. 5, Romo was arrested and charged with corporal injury resulting in traumatic condition and false imprisonment, both felonies, along with misdemeanor charges of resist and obstructing an officer and battery. The charges stemmed from an incident involving a Jane Doe, with whom Romo was said to be in a relationship.
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It's unclear if Mateus was the victim in the December case.
Romo had pleaded not guilty in that case and posted bond.
Aaron Romo, who was on bail for alleged domestic violence, allegedly killed his ex-girlfriend, according to police. (Anaheim Police Department)
The 36-year-old has a history of violence against women, according to court records obtained by USA Today.
A woman in a previous relationship filed a restraining order in September that alleged multiple violent incidents in three states.
There was an alleged attack and rape of her and her friend in April 2022, a violent encounter in Las Vegas in May 2022, and an alleged assault in Arizona that put her in the hospital in August 2021, USA Today reported.
"Detectives believe Romo has assaulted other women in the past and are asking for anyone with previous contact with Romo to come forward," Anaheim police said.
A graph showing a comparison of recidivism rates between suspects who have posted bail vs. those who were released under zero bail policy. (Yolo County District Attorney)
Because the investigation is ongoing, detectives have declined to elaborate on evidence or to discuss possible motives.
Anaheim police and the Orange County Public Defender's Office didn't respond to Fox News Digital's request for comment, Thursday morning.
Police asked anyone with information related to the homicide or Romo to call the Anaheim Police Department at 714-321-3669 or the Orange County Crime Stoppers at 855-TIP-OCCS or www.occrimestoppers.org.