PHOENIX - Police arrested a man Tuesday after he allegedly beat his 2-year-old son because he was upset with the boy's mother.

Joshua Junior Rodriguez, 23, admitted to spanking and hitting the boy with a belt on Oct. 11.

According to police documents, Rodriguez was arguing with the boy's mother as she was packing a bag to leave. He grabbed the bag and threw it, and when the woman turned to leave, she heard a whipping sound.

She turned back around and saw Rodriguez was hitting the boy with the strap of the bag.

When she tried to take the boy away from Rodriguez, he grabbed him by the back of the shirt and threw him on a bed, spanking him more than 20 times, according to arrest documents.

Then Rodriguez took the boy into the shower, took off his diaper and spanked him again more than 20 times, the boy's mother told police.

Documents show the boy had bruising on his buttocks and legs, as well as scratches along his back and neck.

Rodriguez wouldn't let the boy's mother leave the house, saying she would call police.

He was arrested 20 days later and faces one count of child abuse.