A detective with the Englewood Police Department was one of the 515 people who was wounded when a gunman opened fire on a packed outdoor concert in Las Vegas Sunday night, killing at least 58 people.

Det. Curtis Leoni was shot and his family says is going to be ok. He was off-duty at the time, a family member told 9NEWS.

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He was attending the three-day Route 91 Harvest festival that started on Friday and was one of the estimated 22,000 people in the crowd when a gunman started shooting from a 32nd-floor room at the Mandalay Bay Resort and Casino.

Sunday's tragedy is now the deadliest mass shooting in U.S. history.

One of Leoni’s family members told 9NEWS that they were in contact with him early Monday morning and that they are waiting to learn when he will be released from the hospital and what the next steps are.