Allemand, who was taken off life support Wednesday after an apparent suicide attempt, was "an angel," he tells PEOPLE.
"I am in complete shock and devastated to hear the news about Gia," says Pavelka, who romanced Allemand, 29, on season 14 of The Bachelor. "She was one of the sweetest people I have ever known. And a very dear friend. My heart goes out to her family during this very difficult time. We have lost an angel today."
The model and actress, who also appeared on two seasons of Bachelor Pad, was found in her New Orleans home on Monday by her boyfriend, NBA player Ryan Anderson of the Pelicans, her family says in a statement. He called 911 and Allemand was transported to the hospital in critical condition.
Family, friends and fans are mourning the loss of the New York native, who had been working as a Pure Barre instructor in New Orleans, where she lived with Anderson.
"I'm shocked right now," former Bachelorette star Ed Swiderski tells PEOPLE. "I was just with her last week. We were all in New York together and I just can't believe it."
"She could not have been in better spirits when I saw her seven days ago. She could not have been more of a crisp, clean person. She just defined a healthy-looking person."
Swiderski says the Bachelor "family" is at a loss for words.
"Everyone is freaking out," he adds. "I'm getting calls from all over. We're all in shock. She was, it's hard to say 'was' because I just saw her, a beautiful soul. Not only was she a beautiful person, but she was super sweet. She was so full of life. It's just so sad."
Bill Davila / Startraks, Amy Sussman / Getty
Reporting by AILI NAHAS