The brother-in-law of murdered Florida woman Nicole Montalvo is the latest of several former relatives now under arrest as a result of the investigation into her death.

Nicolas Rivera, 28, was apprehended by federal authorities Monday after detectives allegedly discovered child porn images during the Montalvo probe. Rivera, who faces eight counts of child pornography, has been identified as a “person of interest” in the woman's slaying.

Rivera's arrest, however, is only the most recent in a string of arrests of Montalvo's former relatives. Her estranged husband, 31-year-old Christopher Otero-Rivera, Nicolas’s brother, and the pair's father, 63-year-old Angel Rivera, were arrested last week and charged with first-degree murder. They're both being held without bail at the Osceola County jail.

MURDERED FLORIDA WOMAN'S ESTRANGED HUSBAND, IN-LAWS ARRESTED IN CONNECTION WITH BRUTAL KILLING

Authorities also arrested Montalvo’s mother-in-law, 59-year-old Wanda Rivera – Angel’s wife and Nicolas and Christopher's mom – on Friday for allegedly tampering with evidence related to the homicide and providing false or misleading statements to detectives.

Officials told Fox News even more arrests are expected in the coming days. Osceola County Sheriff Russ Gibson emphasized that Montalvo’s murder, which he said is believed to have been pre-meditated, is the worst case of brutality he's seen in his more than three-decade law enforcement career.

The 33-year-old Montalvo, known to many in her community as a smiling employee at Broadway Pizza Bar in Kissimmee, was reported missing Oct. 23. She had dropped off her 8-year-old son, Elijah, at the St. Cloud home of his father, Otero-Rivera, two days earlier but failed to return to pick him up. On Oct. 25, investigators reported discovering human remains at a property belonging to Montalvo’s in-laws and authorities confirmed the remains as belonging to Montalvo soon after.

GET THE FOX NEWS APP

Montalvo reportedly had been a victim of domestic violence and had sought legal protection from Otero-Rivera. Her murder came while Otero-Rivera was still on probation as part of a plea deal he accepted after attacking Montalvo the year before.

News of the 33-year-old's murder swiftly sparked outrage among the close-knit community and local law enforcement, who have vowed to seek justice for her family and advocate for stronger legislation to shield other domestic violence victims.