Are these two fires the work of an arsonist (paid off or doing this on his or her own)?

MENDOCINO COMPLEX INCIDENT UPDATE
Date: 7/28/2018
Time: 7:00 a.m.
http://cdfdata.fire.ca.gov/admin8327985/cdf/images/incidentfile2175_3695.pdf

Incident Start Date: 7/27/2018
Incident Start Time: RANCH 12:03 PM & RIVER 1:01 PM (1 hour apart)
Incident Type: Vegetation Fire
Cause: Under Investigation

Total Acreage:

River Fire: 6000
Ranch Fire: 3500

Containment:
River Fire: 2 %
Ranch Fire: 2 %

Expected Full Containment: Unknown

Civilian Injuries/Fatalities: none

Firefighter Injuries: 7 injuries

Incident Location:
Ranch Fire: Hwy 20 MP 39, Old Lake County Hwy, Blue Lake, 8 miles NE of Ukiah
River Fire: Old River Road, 6 miles North of Hopland

Situation Summary:
Fire resources continue to battle the River and Ranch fires. Continued high heat
and steep rugged terrain, combined with critical low relative humidities, in
conjunction with local gusty winds will continue to challage firefighters efforts
today. A Red Flag Warning is in effect.

Mandatory Evacuations:
• 8000 block of River Road, South to the intersection of Highway 175 from the Russian River east to the Ridge above Highway 175, within the North South points. These evacuations also include all driveways and homes located between the North South points.

Evacuation Center(s):
Mendocino College, Dance Room at 1000 Hensley Creek Road, Ukiah

Roads: CLOSED: Old River Road and University Road

OPEN: Highway 175 & Highway 20, use caution in the fire areas, watch for emergency vehicles entering and exiting the roadway.