Eighteen-year-old Danielle Marzejka had been missing about two days when swarming flies and a noticeable stink drew her brother to the gruesome discovery of her body where it had been stuffed into a heavy-duty garbage bag in a shed at her home in Clinton Township, Michigan, PEOPLE confirms.
Next to Marzejka’s remains were those of her 19-year-old boyfriend, Seren Bryan, authorities say.
It didn’t take long before investigators zeroed in on their suspected killer: Marzejka’s 24-year-old brother, Robert Marzejka Jr., according to Clinton Township police Capt. Richard Maierle.
Robert, who is now accused of two counts of first-degree murder, was arrested without incident on Wednesday afternoon in a library in Cincinnati, police say.
They believe he fled Michigan — first by van to Toledo, Ohio, then by bus to Cincinnati — at some point early in the investigation or before his sister had been found dead. Authorities were unable to locate him for questioning the night her remains were discovered, Maierle says.
U.S. Marshals had been pointed to Robert in Cincinnati by a local who said he was looking for a library where he could access the Internet to play a game, according to Maierle.
Key details about the homicide case remain unclear as the investigation continues. Causes of death have not been released and Maierle declined to discuss if a weapon or weapons were used. Motive is also a mystery, for now.
“What possessed him to do it?” Maierle says. “We don’t have any idea.”
He says there was no history of domestic incidents involving the family in Clinton. Court records show Robert was the subject of a mentally ill petition in 2015 that was dismissed in January, though it is unclear why.
• Want to keep up with the latest crime coverage? Click here to get breaking crime news, ongoing trial coverage and details of intriguing unsolved cases in the True Crime Newsletter.
Maierle tells PEOPLE the case unspooled over the course of a few days last week, beginning on Aug. 23 when Danielle and her boyfriend, who were living in a mobile home park with brother Robert and their father, Robert Marzejka Sr., returned from their night-shift at a local hot dog chain.
After that, they went missing on Friday — “just disappeared,” Maierle says.
Danielle’s father filed a missing-persons report on Saturday at 6 a.m. The next night, about 8 o’clock, her brother Kevin, who did not live at the mobile home, discovered the remains in the shed on the property. He saw one of their arms and immediately “backed off” from the shed and alerted others.
Police think the slayings occurred at the home, Maierle says, but he declined to be more specific.
Jail logs in Ohio show Robert Marzejka Jr. remains in custody there. On Friday he waived his right to challenge his extradition back to Michigan, Maierle says, and he could return to Clinton within a few weeks.
County prosecutors could not immediately be reached by PEOPLE but, in a brief statement on Facebook, prosecutor Eric Smith said:
“While nothing can take away the pain felt by family, friends, and the community regarding the tragic deaths of Danielle Marzejka and Seren Bryan, my office intends to see that justice is done.”