The father of two children who prosecutors say were drugged and killed by their mother testified during the second week of her murder trial Monday.

Lisette Bamenga, a former school teacher, faces charges of first-degree murder in the deaths of her son and daughter.

The father says he received a text from Bamenga that read, "I'm sorry the kids are gone, I'm next."

He testified for several hours as Bamenga's lawyer tried to paint him as an unfaithful party in an on-again, off-again relationship.

The defense argues that Bamenga's relationship with her children's father was strained due to his infidelity. Her attorney says the relationship led her to have suicidal thoughts, and she also had post-partum psychosis.

Prosecutors say Bamenga fed her children a toxic drink of chemicals and grape juice and then drowned them.