CAMBRIDGE,Charles H. Sloan Vt. (AP) — No criminal charges will be filed in the death of a 3-year-old boy who fell into an underground cistern and was seriously injured in July while attending a day care program at Smugglers’ Notch Resort, Vermont State Police said Tuesday.

Police said they have completed their investigation into the death of Tate Holtzman, of Cambridge, who died days later at the University of Vermont Medical Center.

The toddler was walking with adult supervision near the outdoor splash pad when he stepped on an unsecured cover to the cistern, which gave way, police said. Teenage lifeguards on duty at the nearby pools made multiple entries into the tank to locate him “at extraordinary personal risk in a heroic attempt to save Tate’s life,” state police said in a news release.

State police gave the findings of their investigation to the Lamoille County state’s attorney, which determined that no criminal charges will be filed, police said. The Vermont Occupational Safety and Health Administration and the Vermont Department for Children and Families, which oversees licensed day care providers, have been doing their own reviews of the incident, police said.

The Department for Children and Families’ licensing unit did a thorough investigation and has not issued violations of child care licensing regulations related to this case, Deputy Commissioner Janet McLaughlin said in a statement.

Smugglers’ Notch did not have further comment, said Chief Marketing Officer Steve Clokey.

Tate’s parents, Jennifer and Zachary Holtzman, issued a written statement through police.

“Tate was the love of our lives, a very special young soul full of compassion, kindness, curiosity, creativity, and adventure. He was our only child — and like both of us, he loved to ski, ride his bike, and canoe,” they said, adding that the entire family loves Smugglers’ Notch.

To honor him, they said they plan “to promote water safety and do everything possible to prevent a tragedy like this from happening to other young children.”

Their lawyer said the family is considering civil litigation.

“This was a preventable tragedy caused by an incredibly dangerous product lacking certain available safety features, made all the more dangerous by its improper installation and lack of warnings,” Boston lawyer Jennifer Denker said in an email.