A boulder topped with a pink ribbon and covered in a spray-painted message: "Happy birthday, Isa XX" sits in the driveway of Isabelle Prevost. The 20-tonne stone was left there as a gift by her ex-husband Dany Lariviere, mayor of a nearby municipality.

Paul Chiasson/THE CANADIAN PRESS

A small-town mayor is under police investigation after finally giving his wife a nice, big rock.

Make that his ex-wife. And the rock was a 20 tonne boulder, not a ring.

Dany Larivière, the mayor of Saint-Théodore-d’Acton, east of Montreal, told a French news station that he had dropped the boulder off on his ex-wife’s lawn early Sunday morning. The rock is spray-painted “Happy Birthday, Isa XX” and topped with a big pink bow.

“I had to do something so she’d leave me alone,” he toldTVAMonday morning. “That’s the biggest rock she’ll ever get in her life.”

Larivière was unavailable for comment Monday afternoon.

Quebec Police told theTorontoStarthey were still deciding whether criminal charges could be laid, after Larivière apparently refused to remove the boulder.

“It’s a gift. It’s hers now,” Larivière said. “I did it in the middle of the night. It was a surprise.”

He joked that his ex-wife, Isabelle Prévost, had always wanted a big rock, quipping that this one was between 18 and 24 “carat-tonnes.”

Prévost called police to file a complaint after discovering the delivery Sunday morning.

“The investigation is open,” said Sûreté du Québec spokesperson Sgt. Valérie Bolduc. She said police are considering laying charges of harassment or mischief, as well as possible highway-code violations.

The parents of Larivière’s ex-wife described the incident as “disgusting” and her mother toldThe Canadian Pressthat their daughter was too upset to grant an interview.

In his own interview with a local newspaper, Larivière boasted that police stopped him as he transported the boulder with a front-end loader. He owns a small excavation company in Saint-Théodore-d’Acton.

“They checked my papers, everything was in order, and they followed me and were there at the scene,” he toldLa Voix de L’Est.

Larivière said he spent a substantial amount of money during the divorce in order to share custody of their children and added Prévost has been harassing him.

The couple has been separated three years.

With files from The Canadian Press