A grandmother killed at a gender reveal party on Saturday was hit by shrapnel from a homemade pipe bomb that her family built to shoot out the colored powder, police say.

Pamela Kreimeyer, 56, died after the explosion sent debris flying at her home in rural Iowa, authorities said. She was struck in the head by a piece of metal from 45 feet away and died instantly.

The Marion County Sheriff’s Office confirmed the family had been 'experimenting with different types of explosive material on Friday and Saturday'. Police said the family hoped to post the reveal on social media for loved ones.

A source told the DailyMail.com the party was being held for Kreimeyer's son Brad and his girlfriend, named as Kirstie Rankin.

It is understood the family placed gunpowder in the bottom of a homemade stand that was welded to a metal base plate.

After drilling a hole in the side for a fuse, a piece of wood was placed on top of the gunpowder and colored powder was placed on top of the board.

Tape was then wrapped over the top of the metal tubing, inadvertently creating a pipe bomb.

Pamela Kreimeyer, pictured, was hit by shrapnel from a homemade pipe bomb that her family built to shoot out the colored powder. She died instantly, police say

A source told the DailyMail.com the party was being held for Kreimeyer's son Brad and his girlfriend, Kirstie Rankin, who posted this image to Facebook earlier this month

It is understood the family placed gunpowder in the bottom of a homemade stand that was welded to a metal base plate. After drilling a hole in the side for a fuse a piece of wood was placed on top of the gunpowder and colored powder was placed on top of the board. Tape was then wrapped over the top of the metal tubing, inadvertently creating a pipe bomb

A statement from officers revealed how five family members and the expectant mother gathered and 'placed gunpowder in the bottom of a homemade stand that was welded to a metal base plate'.

It adds: 'A hole had been drilled in the side for a fuse, a piece of wood was placed on top of the gunpowder and colored powder was placed on top of the board. Tape was then wrapped over the top of the metal tubing, inadvertently creating a pipe bomb.

'Instead of the gunpowder shooting the powder out the top of the stand, the stand exploded sending metal pieces flying.

'One of these metal pieces struck Pamela Kreimeyer in the head causing instant death. She was standing with other family members approximately 45 feet from the device. It’s believed that the projectile that struck the victim then continued another 144 yards through the air coming to rest in a field.'

In audio obtained by KCCI an operator can be heard telling authorities: 'You are needed...a pipe explosion that has hit a woman in the head.'

Pam's son Brad, pictured in his Facebook profile picture, is expecting a baby with his girlfriend

Kirstie Rankin posted this image to Facebook earlier this month. It is believed the gender party reveal for was for her and Pam's son Brad

The Marion County Sheriff’s Office confirmed the family had been 'experimenting with different types of explosive material on Friday and Saturday' at the home in Iowa, pictured. Police said the family hoped to post the reveal on social media for loved ones

Sheriff Jason Sandholdt said: 'This family got together for what they thought was going to be a happy event with no intent for anyone to get hurt.

'What ended up happening was that Pamela Kreimeyer, a wife, mother and grandmother was killed by a piece of metal where a metal stand, gunpowder and colored powder were involved.

'This is a reminder that anytime someone mixes these things there is a high potential for serious injury or death; please do not take these unnecessary risks. My condolences go out to the family.'