Earlier, the protesters breached the police barricade and held a program in front of the US Embassy.
The police vehicles literally ran over the protestants who gathered on Wednesday morning in front of the US embassy from Manila.
The roughly 1,000 students and workers gathered at the embassy were from the left-wing activist group Bayan, which has organized mainly peaceful protests in front of the U.S. Embassy for decades.
The protesters had gathered to call for an end to the presence of United States troops in the country and to support President Rodrigo Duterte's statements in favour of a foreign policy independent of the US. The police also lobbed tear gas at a column of protesters who managed to break through the ranks of riot police officers. The vehicle then drives into the crowd several times, injuring a number of people.
Asked if he panicked, Khu said: "Of course, our vehicle was overturning and if they seized control, they could run down other policemen".
The President said he would still "investigate" and get the assessment from Executive Secretary Salvador Medialdea, the Philippine National Police and the Department of Interior and Local Government.
Photos showed a grey-haired man afterwards trapped underneath the stationary van, with his leg and hips under one of the back tyres.
The police and the protesters had different accounts of what happened.
Despite his popularity, the majority of Filipinos have a positive view of the United States - 92 percent of them held a "very favorable" or "somewhat favorable" opinion of the U.S. in 2015, according to data from the Pew Research Center.
"If they see an American, they would kill him". The last speaker was finishing up the one-hour program when police began pushing their shields against the protesters, followed by firing tear gas and the rampaging police mobile.
A police auto rammed into the group several times.
Legal group the National Union of People's Lawyers condemned the police violence, saying that they would help those injured in the protest to file criminal complaints against the force for violating their right to demonstrate.
Palabay slammed the police reaction as excessive, even if a few of the protesters had instigated the violence.
In a rally staged by Sandugo at Camp Aguinaldo yesterday October 18, military personnel also fired water cannons at protesting indigenous peoples and Moro.
The group said the protest was about to culminate when Col. Marcelino Pedroso of the Manila Police District allegedly signaled the dispersal.
Several DPSC police patrol mobile were positioned, along with anti-riot police in front of the U.S. embassy gate. Duterte did not take well to concerns from Washington and other Western capitals about his deadly war on drugs.