HOUSTON -

The ex-boyfriend of a missing woman has confessed to her murder, police said.

Houston police said Mark Castellano, 37, confessed to killing Michelle Warner, 31, during an argument about money. Investigators said Castellano also confessed to driving Warner's body to the Midland/Odessa area and trying to bury it in an oilfield. Castellano helped lead police to Warner's body on Sunday.

Police said Warner suffered a broken neck.

Warner disappeared from her southwest Houston apartment in the 7200 block of Bellerieve along with the couple's 3-year-old son on Sept. 21, sparking a massive search.

Investigators said the 3-year-old boy was at home when his mother was killed.

"When (Castellano) did what he did, and it was quiet again, Cayden, who walked around the corner and looked into the room and saw Michelle's feet hanging off the bed," said Officer Fil Waters with HPD's Homicide Division. "He explained that to Cayden as mommy's asleep."

Police said Castellano fled to the Midland/Odessa area with his son after the killing to stay with family members. He had Warner's body in a container in his car for two days before he dumped it in the oilfield, investigators said.

Castellano flew back to Houston on Sunday and gave a confession after two hours of questioning, police said.. Castellano was charged with murder.

"Quite frankly, in this, if he had not confessed we would still be stuck," Waters said.

Missing woman's body found

Police said while the pair was no longer a couple, Warner moved in with Castellano because she fell on hard economic times, but had recently started a new job as a paralegal.

"This type of relationship, it's like gasoline and water," Waters said. "This was just not the proper mixture."

When reached Sunday by phone, Warner's brother, David Chaffin, told Local 2 he knew the coupled argued but "never thought something like this would happen."

Chaffin said the family had flown to Los Angeles to tape a segment for the Dr. Phil show about Warner's disappearance and found out about the confession "as soon as we hit the ground."

Warner's family members said they are devastated and can't believe they have to tell her 11-year-old daughter and 3-year-old son that their mother is gone.

The children are staying with family.