A Delaware County high school is in turmoil over a racist letter left on several doorsteps last weekend of Swarthmore and a seemingly related photo of two youths in Ku Klux Klan-style hoods that students shared widely on social media — prompting probes by local police and the Wallingford-Swarthmore School District.

The letter, which circulated on Facebook after several residents reported finding it, praised President Trump and Vice President Pence, and told the recipients to leave the United States, claiming, “There is now a law against filthy nutheads like yourself living in our country.”

Students who viewed the photo of two youths wearing white hoods on the social-media site Snapchat on Tuesday, and who believe the photo and the letter are linked, staged a walkout Wednesday morning at Strath Haven High School in Wallingford, Nether Providence Township, that briefly shut down South Providence Road.

School superintendent Lisa Palmer sent parents and other district stakeholders a letter Wednesday saying, “The name and social media handles associated with this photograph appear to be linked to students in our district. However, at this time we don’t have many details and can’t even say who created this photograph and/or social media post.”

According to the Pennsylvania Department of Education, the high school serves a largely affluent population of nearly 1,200 students, 74 percent of whom are white, 9 percent black, 8 percent Asian, and 3 percent Hispanic. Five percent of the students are of mixed race.

Swarthmore Police Chief Brian Craig said at least four students from Strath Haven, all juveniles, have been identified as responsible for the letters, which they sent to four families. The students have written letters of apology. He said the investigation is continuing into whether more students were involved and whether charges will be filed. The letters reportedly were sent to nonwhite families, but Craig said the recipients “were not people of color.” He declined to provide any other information, citing the ongoing probe.

Nether Providence Police Chief David Splain said police are trying to determine the origin of the photo.

The letter, which has been posted widely on social media, states that “Donald and his crew think its best if u pack ur bags tonight” and that for recipients who don’t leave, “then we will either 1) put u up for adoption or 2) execute u and ur kiddos.” The notes also include racist suggestions of moving to a “new Mexico city” and working in jobs such as fast food or prostitution.

“We are extremely disturbed and disappointed at the thought that any of our students might be associated with this kind of vile display of racism,” Palmer said in her letter. “We will very closely follow our district discipline policy as it relates to any student found posting this kind of material on a school device or network, or during school hours.”