RIO DE JANEIRO, Sept. 28 (Xinhua) -- The Brazilian Federal Police announced on Friday that the investigation over the attack on presidential candidate Jair Bolsonaro has ended with a conclusion that the attacker acted on his own.

"On the matter of the participation or authorship at the site of the event, the involvement of third parties is discarded, given the evidence collected," the police said, adding that the action involved "an unmistakable political motivation."

The attacker, identified as Adelio Bispo de Oliveira, was charged with the crime of attacking a person due to political nonconformity. According to Brazil's National Security Law, the criminal is to face a prison sentence of three to 10 years; if the victim is seriously injured, as Bolsonaro was, the sentence doubles.

Oliveira stabbed Bolsonaro with a large knife during a public campaign event in Juiz de Fora, Minas Gerais state, in Brazil's southeastern region, on Sept. 6. According to doctors, the candidate sustained extensive damage to his intestines, which required an emergency colostomy.

Oliveira was arrested immediately and confessed the crime in three different testimonies. After a series of investigation on the attacker, the police said that "strong evidences" showed he had planned the attack days before.

Bolsonaro continues to have the lead over his rivals and the gap between him and the runner-up remains stable, the latest poll showed.?