There is no clear indication of motive yet, but Britain's interior minister said she was "deeply concerned," according to The Associated Press.
The Thames Valley Police included a link to their website with details of the case and a request that the public share any video or photographic evidence, instead of posting it on social media.
The stabbing took place in Reading, at Forbury Gardens around 7 p.m. Police and emergency services were called in following reports of the attack. The officers arrested a suspect at the scene who's currently in police custody.
Injured bystanders were taken to the hospital for treatment. Law enforcement asked the public to avoid the area.
Local residents with knowledge of the suspect, or the crime, are asked to call the Thames Valley Police by dialing 999, "quoting reference 1159 20/6."
The Royal Berkshire Hospital said it treated two injuries, but there was no word on fatalities, The AP reported.
The attack reportedly happened only hours after a Black Lives Matter demonstration at Forbury Gardens, however, one of the event organizers claimed on social media that protesters had cleared out of the area by the time the incident took place.