Ukrainian authorities are looking into whether foreign special services were involved in an assassination attempt against presidential aide Serhiy Shefir, Interior Minister Denys Monastyrsky said on Wednesday.

A volley of automatic gunfire hit a car carrying Shefir on Wednesday, an incident Ukrainian President Volodymyr Zelenskiy said may have been a message intended for him.

A local television station said at least 19 bullet holes could be seen on the driver’s side of the car.

Police said in a statement they had opened a criminal case on suspicion of premeditated murder.

Zelenskiy, who is in New York for the U.N. General Assembly, said he did not know for now who was responsible for the attack, which shocked the country’s political elite.

“I don’t know yet who stood behind this,” said Zelenskiy. “Sending me a message by shooting my friend is weakness.”

Shefir is close to Zelenskiy and leads a group of advisers.

Zelenskiy came to power on a promise to take on the country’s oligarchs and fight corruption, and Mykhailo Podolyak, one of his advisers, said the assassination attempt could be a result of the campaign against the oligarchs.

DOUBLING DOWN

Zelenskiy said he would be doubling down on his planned reforms rather than backing off.

“It does not affect the strength of our team, the course that I have chosen with my team – to change, to clean up our economy, to fight crime and large influential financial groups,” he said.

“This does not affect that. On the contrary, because the Ukrainian people have given me a mandate for changes.”

Podolyak, Zelenskiy’s adviser, promised tougher measures against oligarchs after the attack.