There are new questions in the death investigation of a 4-month-old boy, and the man who police think can answer those questions is nowhere to be found.

The search is on for 24-year-old Joseph Lamay, the man who was last seen with Lorenzo Hernandez. Brevard County Sheriff's Office deputies responded around 1 a.m. Friday to an apartment in Palm Bay after Lamay called 911 to report Hernandez was unconscious and not breathing.

The child was taken to an area hospital, where he was pronounced dead.

Lamay hasn't been seen since, police said. Lamay isn't a suspect in the baby's death at this point in the investigation, police said.

He was babysitting while the child's mother, Chastity Cintron, was at work. Cintron said Wednesday that she is "heartbroken."

"I don't have anything to say," she said. "I just want my baby back."

Family members said they haven't seen Lamay since Friday.

"I mean, you're talking about a small child, a defenseless person who, if somebody hurt that deliberately, we want to know," said Yvonne Martinez, a spokeswoman for the Palm Bay Police Department. "It's our job as a law enforcement agency to make sure justice is done."

Police on Tuesday issued an arrest warrant for Lamay on an earlier probation charge. Investigators hope Lamay can provide answers as to how the child died.

"We just want him to come forward so police can ask him a few more questions to find out what really happened to (the child)," said Frank Cintron, the child's grandfather. "That's all we really want so we can put this behind us and have some closure."

Lamay has a criminal past that includes domestic violence battery, theft and heroin possession.

Anyone with information on Lamay's whereabouts is asked to call the Palm Bay Police Department at 321-952-3539.