MILFORD, Mass. (AP) — A 10-year-old Blackstone boy went into cardiac arrest during a swimming test at a Milford pool and later died, police and relatives say.

Alexander Cora died Monday night at UMass Memorial Medical Center in Worcester, Chief Thomas O'Loughlin said. He apparently had an undiagnosed heart condition that led to his death, his aunt Amy Kurzontkowski told The Milford Daily News (http://bit.ly/TSm8wX ).

Alex was visiting his grandmother in Milford on Sunday when the two went to the pool.

The boy was under the supervision of a lifeguard for a test to see if he could swim the length of the pool, the chief said. He went into distress about halfway across and was pulled from the water by the lifeguard. He had a pulse when he came out of the water.

He was taken to Milford Regional Medical Center, stabilized and then airlifted to UMass Medical Center.

His aunt called him a "goofball" who loved reading, swimming and playing video games. She also said he was a devout Catholic who kept a Bible by his bed.

"The child had a heart of gold," she said. "He was an amazing kid."

___

Information from: The Milford (Mass.) Daily News, http://www.milforddailynews.com/