Without warning, a silent killer visited a pastor in Florida while he was singing during service on Sunday.

Pastor Jim Watson of Crossroads Family Fellowship in Clermont, Florida collapsed after singing "In His Presence," Charisma News reported.

The killer? A "widowmaker" heart attack. According to medical experts, this kind of heart attack occurs when the left anterior descending (LAD) coronary artery closes completely, resulting in immediate death.

Before he suffered the fatal heart attack, Watson had told his wife Linda that the Holy Spirit had prompted him to sing "In His Presence," a family friend told Charisma News.

Watson's death stunned members of his family, fellow church workers, congregants and family friends.

"Pastor Jim was a true gentleman and oozed the love of Jesus on everyone he met," said Pastor Steven Halford. "I had never met a man more gifted in the role of pastor/shepherd as I had Jim Watson."

Halford pastors a church in England where he and his wife modelled their pastoral team after Jim and Linda Watson.

"He was a loving husband, father, brother, son, pastor and of course, friend. He took me in and loved me and gave me a chance when few others did. I love you, Pastor Jim. I'll be seeing you," Halford said.

Watson leaves behind his wife, three children and a number of grandchildren.

Watson was an ordained minister with Evangel Fellowship International, chaplain for the Central Florida Christian Bass Club and a founding member of the South Lake Pastor's Fellowship.

The Watsons' Crossroads Family Fellowship is a non-denomination church affiliated with Vision Christian Bible College, Kenneth Copeland Ministries, and the South Lake Pastor's Fellowship.

As written in its website, the church seeks to equip "people of all ages to respond to the leading of the Spirit, using them in ministry and praise and worship."