Three cardboard cutouts of black men were found hanging by nooses on Saturday on the Berkeley campus of the University of California.

A school spokeswoman, Amy Hamaoui, said police were trying to determine who had placed the effigies, which were found at two prominent campus locations on Saturday morning.

Hamaoui said the effigies appeared to be connected to a noontime demonstration nearby planned to coincide with a national protest against police brutality dubbed “#blacklivesmatters”. The effigies appeared to be life-size photos of lynching victims.

The effigies had names of lynching victims and the dates of their death. At least one effigy had “I Can’t Breathe” printed on the front. Hamaoui said it was unclear who had placed the effigies.

“We are unsure of the intent,” Hamaoui said.

Two of the effigies were removed by police and a student took down the third. Organisers of the Berkeley protest were mystified as well.

“We just hope it’s someone who wanted to bring attention to the issue,” said Spencer Pritchard, 21, a Berkeley student and an organiser of the demonstration. Pritchard said about 200 protesters demonstrated in Berkeley with the goal to “disrupt business as usual to show that black lives matter”.

Pritchard said many of the Berkeley protesters planned on attending a demonstration against police brutality starting in Oakland at 2pm PST. A similar demonstration was scheduled at the same time in San Francisco.