Police arrested Michael Dunn on Saturday after the couple's 3-year-old drank the allegedly tainted drink on Halloween night.

According to the criminal complaint, Dunn, 43, said he and his wife had been arguing over bills, and he put half a tablet of Lexapro in the tea to calm her down.

She is a Milwaukee police detective and discovered the medicine when she saw white powder around the 3-year-old's mouth. A little earlier, she had given the child some of her tea to warm him after trick-or-treating.

When she confronted Dunn, he denied putting anything in the cup and said the substance was undissolved sugar, the criminal complaint said.

According to the complaint, she saved the substance and then found Dunn's prescription for Lexapro. When he admitted to putting it into her tea, she called police.

Michael Dunn is an 18-year veteran of the Milwaukee Fire Department. His firehouse, at 64th Street and Fairview Avenue, offered little information on Monday, and only told 12 News it was told to carry him on sick leave.

This is not Dunn's first domestic abuse arrest. Court records reveal a 2004 arrest involving his former wife. Dunn threw a bag of laundry at his 5-year-old daughter and then threw his wife to the ground, police said. As part of a so-called deferred prosecution agreement, the district attorney dropped the charge after Dunn stayed out of trouble for seven months.

Dunn remained in the Milwaukee County jail where he was booked on the felony charge of placing foreign objects in edibles.

The prosecutor said both the wife and child were unharmed.