Ugandan legislator Francis Zaake, detained after the president’s convoy was stoned, has been “brutalised” by security personnel, an opposition figure said on Wednesday as images of the bruised lawmaker emerged on social media.

Supporters of an independent candidate running in a parliamentary by-election threw stones at President Yoweri Museveni’s motorcade on Monday in the West Nile region near the border with the Democratic Republic of Congo, police and Museveni said.

Police used tear gas and shots to halt the stoning and detained at least five members of parliament along with several other people.

Those arrested included Robert Kyagulanyi, an independent lawmaker and musician who has gained popularity since he joined parliament in 2017 through scathing criticism of Museveni’s government, sometimes expressed through music.

During Monday’s incident, Kyagulanyi’s driver was shot dead, according to police who have said they are not yet able to identify who shot him.

Mugisha Muntu, a former head of Forum for Democratic Change (FDC), Uganda’s biggest opposition party, said on Twitter.

“Hon Zaake was badly brutalised by security forces journalists too weren’t spared. We must reject this lawlessness.”

Images circulated on WhatsApp and Facebook showing Zaake apparently lying on a bed, eyes closed, with a swollen face.