And, the source says Park Police didn't know President Trump would be walking across the park several minutes later.
This same church was gutted by fires during Sunday night's riots.
"I am your president of law and order and an ally of all peaceful protesters, but in recent days our nation has been gripped by professional anarchists, violent mobs, arsonists, looters, criminals, rioters, Antifa and others", Mr Trump said during a nationwide address as tear gas went off and crowds protested in the streets nearby.
But there was relative calm in Minneapolis, where the uprising began following the May 25 death of George Floyd, an unarmed African-American man who was pinned down for almost nine minutes under the knee of a white police officer, who ignored his pleas for his life.
"If I'm not over here messing up my community, then what are you all doing?" he said. He then walks back to the White House.
"I have strongly recommended to every governor to deploy the National Guard in sufficient numbers that we dominate the streets", he announced.
Floyd died last week after he was pinned to the pavement by a police officer who put his knee on the handcuffed black man's neck until he stopped breathing.
President Trump wanted to walk from the White House through the park to the Episcopal church.
"He will not have died in vain, but we can not allow the righteous cries of peaceful protesters to be drowned out by an angry mob", he said.
Smith beating up a protester for allegedly breaking his truck's window
According to TMZ , Smith parked his truck in a residential area, located near the Flight Club on Fairfax Ave. Floyd, a black man, died after white officer Derek Chauvin kneeled on his neck for several minutes.
"This was done in a time of deep hurt and pain in our country, and his action did nothing to help us or to heal us", added Curry, the first African American to hold that leadership post for U.S. Episcopalians.
The president, accompanied by his daughter Ivanka, several Cabinet members and Secret Service agents, walked to St. John's almost 30 minutes before Washington's just-installed 7 p.m. curfew was to begin - timing that added to the chaos and confusion among demonstrators and that incensed Mayor Muriel Bowser.
Many other peaceful protests are also underway mourning the death of Floyd at the hands of police in Minneapolis and demanding an end of police violence directed at blacks and other minorities.
The gathering was part rally and part impromptu eulogy as Floyd urged people to stop the violence and use their power at the ballot box. He tear-gassed peaceful protesters and fired rubber bullets.
"For our children, for the very soul of our country, we must defeat him". I mean, it was shameful.
On a Monday call with governors and law enforcement officials, Trump delivered his most strident message yet as cities across the country impose curfews and governors deploy the National Guard to try to head off another destructive evening.
NY governor Andrew Cuomo also expressed outrage over the incident.
"The president is calling out the American military against American citizens", he tweeted.
The Posse Comitatus Act is an 1878 law that prohibits the government from using military forces to act as a police force within U.S. borders.
"This president has repeatedly proven he is incapable of governing and shown nothing but false bravado throughout the chaos that has accompanied his time in office", Inslee said in a statement.
"The Insurrection Act requires that a governor ask the federal government to have federal forces brought in", said Illinois Governor J.B. Pritzker, a Democrat, said on MSNBC on Monday night.