After successful treks across Europe and its native Canada, a child-size hitchhiking robot had made its way via rides with friendly humans all the way from Boston to New York City to the streets of Philadelphia.
Whereupon, its makers say, it was mugged and dismembered on Saturday.
The Canada-based creators of "hitchBOT" said they received the dispiriting news when they received a photo Saturday night of the smashed-up robot. They believe someone took it apart early Saturday morning.
HitchBOT already had a dedicated fan following on social media, where users often posted photos of themselves giving the pint-size bot - "Hitchy," as one admirer called it - a ride or tour of their city.
HitchBOT was created by Canadian researchers as a social experiment: After it had hitchhiked across Canada for 19 days last summer, the plan was for it to travel from Boston to San Francisco this month.
But that plan ended, apparently, in the City of Brotherly Love.
In a photo circulating on Twitter, hitchBot is visibly dismembered. The bright yellow hands have been signed by fans, who probably drove hitchBOT around not long ago - but its blue foam arms, which resemble a pool noodle, lay detached from the body.
In a message from "the family" of hitchBOT on the project's website, researchers wrote: "Sometimes bad things happen to good robots."
David Harris Smith, a co-creator of hitchBOT, said Sunday that he and his team don't plan to file a police report.
Indeed, Philadelphia police said no one has filed one.
"I spoke with both Center City districts and police radio, and at this time no there are no reports of this," Officer Tanya Little, a Police Department spokeswoman, said by e-mail. "They are all seeing the same tweets and other social media posting as you are. . . . If you get an exact location that would be helpful, as well."
That location might be in the vicinity of the city's fabled oldest street. Elfreth's Alley is where YouTube regular Jesse Wellens of Philadelphia says he dropped off hitchBot just before 5 a.m. Saturday.
"I feel somewhat guilty," Wellens said Sunday evening at Elfreth's Alley and Second Street, pointing to the bench where he says he left hitchBOT.
"But I did what it said," Wellens added. "And I sat here with it until 6 a.m."
He was referring to the purpose of the social experiment - to drop hitchBOT roadside and let him hitchhike - that he'd looked up online.
On Saturday at 3:39 a.m., Wellens tweeted a photo of himself and fellow YouTuber Ed Bassmaster with the robot in his car. Just before 5, he followed up by tweeting that he'd dropped hitchBOT off at Elfreth's Alley - for another driver to pick up.
Most other people, Wellens thinks, have been handing hitchBOT off to other robot fanatics, rather than leaving the bot alone for extended periods.
But Wellens decided to stay true to the nature of the experiment. He tweeted to his 890,100 followers that he'd left hitchBOT at Elfreth's Alley after staying with it for hours and then continued to monitor the bot's location online.
Around 6:30 a.m. Saturday, when the battery stopped working, is when the attack on hitchBOT is thought to have occurred.
"Thanks Philly!!! You freaking Killed @hitchBOT I'm so mad right now," Wellens tweeted Saturday upon hearing the news.
The Canada-based scientific team behind hitchBOT's journeys told the Associated Press on Sunday that it doesn't know who destroyed the robot or why. The team said it can't track the robot's location at the moment because its battery is dead, the AP reported.
"Sadly, sadly it's come to an end," Frauke Zeller, another one of hitchBot's co-creators, told AP.
Avery Gilmore, 9, and his mother, Jane Shore, of Center City, were walking on Elfreth's Alley on Sunday, contemplating hitchBOT's fate. Gilmore, a robotics aficionado who's in Lego robotics camp at the University of Pennsylvania this summer, had a hard time imagining anyone being afraid of the small robot.
"Having a robot in the car would be awesome," he said. Shore said some family friends even planned to give hitchBOT a ride to Pittsburgh.
Elfreth's Alley resident Stanton Newman said no one he knows of on the historic street saw anything, himself included. He suspects scrappers disassembled hitchBOT for any possible hardware.
Wellens, for one, said he'd like to see security footage from the area to "expose the person" who attacked hitchBOT.
"I'm already on the case, Philly," he said Sunday, adding that he hopes the researchers "just make it better and bigger."
The robot was immobile on its own, but people gave it rides. Created by students and faculty at three Canadian universities - McMaster, Ryerson, and the University of Toronto - it had been in the United States for a little over two weeks, visiting sites around Boston (including a Red Sox game) and New York City, thanks to rides from humans.
And hitchBOT was no unseasoned hitchhiker. It was well-versed in the nomad lifestyle, having traveled safely last year through Germany and the Netherlands.
Despite its apparent demise, hitchBOT tweeted on Saturday night, "My trip must come to an end for now, but my love for humans will never fade."