Eyewitness testimony from a Portland police informant with a history of providing "credible and reliable information on multiple prior investigations" is one of Multnomah County prosecutors' strongest pieces of evidence in charging a 19-year-old woman with arson for allegedly setting fire to the Portland Police Association headquarters.

On Wednesday, the district attorney's office filed charges of arson, criminal mischief and felony riot against Alma Raven-Guido. The charges follow an April 13 protest against racist policing where some of the protesters marched to the union hall on North Lombard Street and set fire to a portion of it.

The most substantial information in the probable cause affidavit filed Wednesday by the Multnomah County District Attorney's Office comes from the alleged firsthand account of an unnamed informant.

"The informant observed the defendant pour a flammable liquid on the building from three plastic bottles which the informant described as having labels which were either blacked out or taped over with black tape," the affidavit says. "The informant further explained that when the defendant was pouring the liquid on the fire and causing the fire to grow, one of the bottles caught on fire and started to melt."

The informant allegedly witnessed Raven-Guido place all three bottles into her backpack, court records say.

Portland Police officer Ken Le told prosecutors that after a large fire was reportedly ignited, "police obtained information from an informant that the defendant was one of the people responsible for the fire."

The informant reportedly provided a description of Raven-Guido and her alleged "actions associated with the fire," court filings say. Officer Le then arrested her with the assistance of Officer Ryan Potter, according to the affidavit. They then searched Raven-Guido's backpack, where they reportedly found lighters and plastic bottles containing "what appeared to be an accelerant." Prosecutors allege that one of the bottles they recovered was partially melted.

According to the affidavit, Portland Fire & Rescue Lt. Jason Anderson was allegedly present during an interview with the informant.

"Lt. Anderson reports that the informant has no criminal convictions, has a history of providing credible and reliable information on multiple prior investigations, and that the informant personally observed the action of the defendant," the affidavit says. "In particular, the informant told Lt. Anderson that the defendant was present when the second large fire began."

The probable cause affidavit does not mention video or photo evidence that reportedly shows Raven-Guido lighting the fire, nor does it mention accounts from other witnesses besides the informant.

The arson burnt a plywood-covered doorway to char. No one was inside the building at the time.

In a reversal of the typical dynamic PPA executive director Daryl Turner issued a muted statement, but all five members of Portland City Council fiercely denounced the arson.

"Burning things, breaking things and attempting to injure police puts lives at risk. I condemn those who were involved in these criminal acts," Mayor Ted Wheeler said during a City Council meeting Wednesday morning. "For those who engage in criminal destruction and violence: Please know that our investigations continue and we're doing everything we can if you've been involved in this kind of criminal destruction to identify you, to find you, to arrest you, and to hold you accountable."

Later in the afternoon, all four city commissioners issued a joint statement.

"We must condemn racial profiling and police violence just as strongly as we condemn indiscriminate property damage and the normalization of arson," the commissioners wrote. "We cannot and should not tolerate violence, and we cannot and should not continue to defer our dreams for a more equitable, inclusive, and just city."